Statcast park effects show the observed effect of each displayed stat based on the events in the selected park. Each number is set so that “100” is average for that metric, and the park-specific number is generated by looking at each batter and pitcher, controlled by handedness, and comparing the frequency of that metric in the selected park compared to the performance of those players in other parks.
For example, the 135 HR mark for 2018-2020 at Great American Ball Park does not mean the Reds hit 35% more home runs at their home park. It means for batters and pitchers who played both at GABP and elsewhere, 35% more home runs were observed at GABP.
⤷ Click Venue Name Below for an Advanced Breakdown of Venue